Fair Value Measurements (Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021
Financial assets:
Cash and cash equivalents	$ 1,825		$ 2,644
Investment in equity securities	19		21
Warrants, fair value	136	$ 136	138	$ 144	$ 143	$ 142
Financial liabilities:
Non-recourse debt	824		1,086
Carrying Amount [Member]
Financial assets:
Cash and cash equivalents	1,825		2,644
Investment in equity securities	19		21
Warrants, fair value	136		138
Financial liabilities:
Non-recourse debt	848		1,115
Fair Value, Inputs, Level 1 [Member]
Financial assets:
Cash and cash equivalents	1,825		2,644
Investment in equity securities	19		21
Warrants, fair value	0		0
Financial liabilities:
Non-recourse debt	0		0
Fair Value, Inputs, Level 2 [Member]
Financial assets:
Cash and cash equivalents	0		0
Investment in equity securities	0		0
Warrants, fair value	0		0
Financial liabilities:
Non-recourse debt	0		0
Fair Value, Inputs, Level 3 [Member]
Financial assets:
Cash and cash equivalents	0		0
Investment in equity securities	0		0
Warrants, fair value	136		138
Financial liabilities:
Non-recourse debt	$ 824		$ 1,086